Originally posted February 2, 2011
Because sometimes side-reactions are a good thing
February 2, 2011
Pizza. God’s gift to humanity. It’s what we turn to when dinner doesn’t go right. It’s where I turn to when I want something comforting. It’s what I want when I go out for a fun dinner. It’s what I find myself in the mood for when I go out for a nice dinner. Pizza is my friend. And, if I may be so bold as to presume your preferences, I bet pizza is your friend too.
Image source. A wonderful comic from the un-equalled xkcd.com. The best part about this flow chart is that you get to order pizza every day.
But, of course, you don’t have to order pizza. Turns out that you can make pretty good pizza at home. Ensuring good toppings seems pretty straightforward. Buy cheese that you like. Get pepperoni/sausage/vegetables that you know taste good. That part is easy. The most difficult parts for many pizza makers at home are getting good pizza dough and baking the pizza at high enough temperatures. I’m not going to get into the perfect temperature to bake your pizza today. I will just say that, in general, the hotter the better. And, by hotter, I mean hotter than a normal oven can get. Jeff Potter gives some ideas for hacking your oven in Cooking for Geeks. The best includes disabling your oven’s lock (and it’s warranty) so that you can bake your pizza in “oven clean” mode. While this may be tempting, there may be a way to develop a good crust that doesn’t involve voiding your warranties or potentially burning down your house.
Making a good dough
An article in the New York Times by Oliver Strand (a former pro-cook who now writes about food) from May of 2010 describes a method for making a flavorful crust that turns a gorgeous golden color upon baking in a standard oven. (See the recipe here.) There are two keys to developing the flavors. The first involves using a sourdough starter. The second involves letting the dough rise and develop flavors over the course of 24 to 48 hours.
Image source. The two pizzas were made with the same dough. The only difference is that the paler crust on the left came from freshly prepared dough while the crust on the right came from dough that was allowed to rise for a full day. (Hungry yet?)
The point of using a sourdough starter is to develop a bolder flavor in your pizza crust. Regular bread depends only on yeast for rising the dough and for flavor development. Yeast cells can bring about these changes because they turn the sugars, which are present in flour, into ethanol (grain alcohol) and carbon dioxide (the gas that makes the dough rise). Sourdough starters rely on both yeast and bacteria for flavor development. The yeast serves the same purpose here. The bacteria turn glucose into lactic acid (yes, this is the same lactic acid that causes you to feel cramping during exercise). The lactic acid gives the characteristic sour flavor to … sourdough breads.
Fermentation of glucose by bacteria into lactic acid (top two reactions) and fermentation of glucose by bacteria into ethanol and carbon dioxide (bottom reaction). To see a larger image click here.
The second key part of the recipe is time. Time does two really important things here. First, it allows gluten (the protein complex that gives dough its elasticity) to develop. Second, and most importantly for this recipe, the long rise time allows new flavor molecules to develop in the dough. The reason why this happens is described in the picture below:
To see a larger image click here.
The bacteria and yeast are meant to perform the two reactions at the top of this image. They have evolved specifically to do this. However, because no organism is perfect, and no chemical reaction is perfect, the yeast and bacteria can “mess up” at times and facilitate chemical reactions that are really not expected. In the case of this recipe, these “side-reactions” produce new flavor molecules. The other important thing to note is the amount of time these reactions take to occur. Because the fermentation reactions are “supposed” to happen, they occur very quickly. The side-reactions that produce the new flavor molecules take a much longer time to develop. This is why the recipe calls for the dough to develop over a long period of time. In order for you to notice these new flavor molecules, you have to give the dough one to two days to rise.
You can actually see the difference in a dough that has developed over a longer period of time. The dough starts to take on a golden color. Generically, this is called caramelization. Although I don’t know if this is the same chemical process that goes on in making caramels or in the Maillard reaction (the browning of proteins – think seared steak – an important topic that I will cover on a later date). The caramelization reactions and Maillard reactions only work at high temperatures (330oF/165oC and 250oF/120oC – numbers from On Food and Cooking). However, the yeast and bacteria may have enzymes that can catalyze these types of colorations. Because I am not entirely sure, I won’t rule out that possibility that the browning seen in the rising dough is the same as what happens when you caramelize sugars and brown meats.
No matter the specifics of what is actually happening, these side-reactions really do give the crust a more complex and appealing flavor. As a chemist, side-reactions keep me awake at night in cold shivers. In the lab I want to produce a specific molecule as cleanly as possible. If side reactions do occur, I have to spend an inordinate amount of time purifying the one chemical that I want out of the complex mixture. (Many chemists spend a good 80% of their time in lab just trying to purify the molecules they have made. Separations are the bane of our existence.) In cooking, many times the opposite is true. Chemical complexity is a quality that we unknowingly strive for while we are cooking. Complexity is what can turn a good dish great. And this pizza dough recipe is one application of chemistry to maximize the complexity (and yumminess – the most scientific term I can come up with at the moment) of what we eat.
Even though this recipe calls for me to foster side-reactions, I’m comfortable with doing this chemistry for the sake of making a fantastic pizza. Now, if only I felt the same way about dismantling my oven …
Cheers
-mrh
Now .. as far as stretching this dough is concerned here’s a video explaining how to do that by pretending you are a DJ:
Watch me!!
I fully expect Alex and Kyle to be experts at this!
Pizza sounds SO much better than exercising
Hmm, side reactions, eh? That definitely is different than the desired outcome in lab. Another difference I’ve noticed between labwork and cooking – when cooking you never get 30% yield and wonder where your mass balance is.
Thanks for the interesting post!
I’m ready for you to make pizza! Now we just need to find the perfect recipe for making our own mozzarella. Got any chemistry magic there?
To add one last point to that descriptive (and tempting) first paragraph: pizza was the dinner of choice on many- but not all- Friday nights through my two years of postdoc-ing at Penn State. After a long, long week in the lab filled with the “joys” that come with being a postdoc, on those Friday nights when I couldn’t stand to cook another meal, it was Papa John’s pizza for me.
I’ve recently begun to find this sort of thing fascinating. Working with lactic acid bacteria on a daily basis- albeit for uses other than alcohol and dough- it’s nice to appreciate it’s more commonly known qualities.
Random note: I only recently found out that sourdough bread originated in my hometown of SF. It’s so common there I never thought it was special or unique so I don’t find that I crave it or go nuts about it (Jack In The Box uses it for like half of their burgers). Then I read an article about “must-have” treats from certain locales and SF sourdough was one of them. Interesting stuff.